Recently, in order to minimize climate change around the world due to the use of fossil fuels, attention has been focused on use of natural energies such as solar energy is or wind energy. One representative example is the use of solar cells which convert solar energy into electrical energy.
A solar cell uses a photoelectric effect that involves converting light energy of the sun into electrical energy. The photoelectric effect has been derived while searching for the reasons why electrons are generated from a metal plate that is exposed to light, and is proof that light has the characteristics of particles. Light particles are referred to as photons, and photons in motion collide with a metal plate of a solar cell to generate positive electrons corresponding to kinetic energy of the photons from the metal plate, and a solar cell stores the generated electrons.
Factors that affect efficiency of a solar cell are, for example, an amount of solar light reflected by a surface of a solar cell and loss due to internal resistance of a solar cell. A surface of a commercialized solar cell is usually formed of iron reinforced glass or epoxy resin. About 10% of reflection occurs on glass that is not anti-reflection coated (AR coating) or on epoxy resin. The amount of electrical energy generated in a solar cell that is lost as thermal energy due to electrical resistance of the solar cell is also considerable. In addition, the solar cell does not convert light of all wavelengths because a conversion rate of light differs according to wavelengths.
Accordingly, although not all incident light energy is converted into electrical energy, apart from the research into this, electrical energy that is once generated has to be relayed to a charger without any loss such as leakage. According to the conventional art, electrical energy accumulated in a solar cell, that is, electrons, are not relayed to a charging cell and thus a ratio between the number of the generated electrons and the number of electrons used in charging is considerably low, and this further reduces conversion efficiency.